Laser Sensor System Scans Railway Tracks

To keep the track infrastructure safe, railway operators need to acquire many track parameters in regular intervals. Irregularities in the rail geometry can cause sudden cracks in the steel rails, since these are under high tensions. These cracks in turn can initiate domino effects, with rails and railway sleepers tearing over large stretches. An innovative optical sensor system surveys the tracks quickly and safely. A laser scanner acquires geometrical irregularities and transforms them into 3D images.

Today the state of the art in surveying a railway track infrastructure appears in camera-based systems. These systems however have a number of drawbacks: The quality of the results heavily depends on the lighting conditions, and they require a rather complex processing of image data. In addition, the image data demands a very large memory space.

In its Rail Track Scanner (RTS), Fraunhofer IPM utilizes, for the first time, a laser scanner to measure rails, railheads, sleepers, and the rail bed. The specific optical design allows the scanner to be mounted just 1.2 meters above the rail bed. The device scans the tracks transversely to measure vehicle movement at a track width of some 1.7 meters. With up to 2 million single measurements per second, the instrument generates up to 800 profiles, providing a detailed three-dimensional image of the tracks and the infrastructure that is associated with them directly. Out of the cluster of points generated, appropriate algorithms extract parameters such as distance, height, and tilt of the rails, as well as the exact geometry of the railheads. These parameters then are compared with set values. The scan frequency can be adapted to the respective task. Topographic structures and deviations are identified at an exactness of less than 1 mm.

The scanner is the size of a shoebox and thus can be mounted to any rail vehicle. Thus, the RTS offers a cost-effective option to survey the rail infrastructure automatically without the need to acquire a specific measurement vehicle. Utilizing an eye-safe infrared laser (class I), the scanner can be deployed in the public space without any restrictions. The instrument, which will be introduced to the public at the Innotrans trade fair in September, will be utilized by Swiss mobile mapping services company iNovitas to survey narrow-gauge lines in Switzerland.

I'm interested in the kind of information that the scanning system can obtain. The image looks like a monochrome (green) image of the scene. Obviously this could be useful if the tracks had been sabotaged or suffered gross damage such as the bed being washed out by a flood, missing rail spikes, or severe physical damage to the rail. Does this technology have any value in detecting progressive material failures? Which of the failure modes that require repair can it detect?

@prabhakar_deosthali: "...This practice is followed only for select trains running in sensitive areas where the incidents of manual disruption of rail tracks have happend in the past..."

Okay I understand the context which you described earlier. I did not know that such arrangement was made due to unfortunate miscreants caused by anti-socials. Good to know that this practice saves many lives, for which the cost of running an extra engine for certain trains in certain areas is insignificant.

This practice is followed only for select trains running in sensitive areas where the incidents of manual disruption of rail tracks have happend in the past.

Just last month a major train accident was averted by such a pilot engine . A section of the track had been blown aprt by explosives and the pilot engine completely derailed while going over it. But it averted a major accident for the train which was to run on that track an hour later.

What you have seen in your childhod is right - those small inspection carts can do this job but they are slow speed and can hinder the high speed train trafiic.

With the kind of laser scanning talked about in this blog a simplified light weight but high spped tracking by an unmanned light vehicle can be a possible solution.

@prabhakar_deosthali: "...a pilot engine runs ahead of the train to ensure that there is no track fault or any other obstruction.."

Is that what followed in India? I do not have much idea, but I think that would be a costly affair as an engine per one high speed train would be engaged all that time just to monitor cracks. I have seen a small four wheeled cart carrying people and pushed by a couple of persons slowly on the tracks in my childhood. I believe that was used earlier to monitor the tracks manually long time back. It was done for each sections of every division...can't imagine the number of people engaged into this. Now a days I believe a specialized track monitoring car is used as shown in the link below:

With this laser based device mounted on the engines (may not be for all) of regular trains for scanning the tracks it would be possible to get rid of those special monitoring vehicles or manual effort. Also the scanning could be done much more frequently that it is currently done. Great piece of equipment.